1. Field of the Invention
The present invention relates to a heating apparatus for heating a substrate on which a coating liquid has been coated, and a coating and developing apparatus including the heating apparatus.
2. Background Art
As an apparatus for forming a resist pattern on a glass substrate for use in a semiconductor wafer (hereinafter, referred to as “a wafer”) or an LCD (Liquid Crystal Display), a coating and developing apparatus is used, which coats a resist on the wafer and then develops the wafer after exposure. In this apparatus, a heating apparatus is incorporated, which is also referred to as a baking apparatus and serves to dry a solvent of a resist liquid, for example, in an apparatus for heating a wafer on which the resist liquid is coated.
With such a heating apparatus, we have attempted to perform a heating treatment by forming an air current passage by covering a region above a heating plate for heating a wafer with a cover, and forming an air current flowing in one direction from one end opening to another of the passage, i.e., the so-called one-way air current. By achieving this heating treatment utilizing the formation of such an air current, attachment of sublimates, to be produced from sublimation from the resist liquid, onto a wafer W as particles, can be reduced.
FIG. 16 depicts one example of a heating apparatus for forming the one-way air current as described above. In the drawing, reference numeral 10 denotes a housing, 10a designates a carrying opening for a wafer, and 10b denotes a shutter for opening and closing the carrying opening for a wafer. Also, in this drawing, reference numeral 11 is a base plate, 12 denotes a heating plate, and 13 is a cooling plate which is movable on the base plate 11 toward the heating plate 12 and adapted to cool a wafer W. On the base plate 11, a gas supplying portion 14 is provided on the front side of the heating plate 12, while a gas exhausting portion 15 is disposed on the back side of the heating plate 12.
In the internal space of the base plate 11, lifting mechanisms 16, 17 for raising and lowering pins 16a, 17a are provided. By the raising and lowering of the pin 16a using the lifting mechanism 16, a wafer W is transferred between the cooling plate 13 and an external carrying mechanism (not shown) which will enter the housing 10 through the carrying opening 10a. Similarly, by the raising and lowering of the pin 17a due to the lifting mechanism 17, the wafer W is transferred between the heating plate 12 and the cooling plate 13. Further, in the drawing, reference numeral 18 denotes a cover-like top plate which can be raised and lowered by a lifting mechanism 18a. 
In such a heating apparatus, as shown in FIG. 17(a), the wafer W is transferred to the cooling plate 13, with the heating plate 12 being covered with the top plate 18 as well as being heated to a predetermined temperature. Next, as shown in FIG. 17(b), the top plate 18 is raised, the cooling plate 13 is then moved into between the top plate 18 and the heating plate 12, and the wafer W is transferred from the cooling plate 13 to the heating plate 12. Thereafter, as shown in FIG. 17(c), the cooling plate 13 is retracted to a position to adjoin the heating plate 12, and the top plate 18 is then lowered to such a position that it is located slightly above the heating plate 12. In this state, a gas is supplied from the gas supplying portion 14 while discharging it via exhausting portion 15 so as to form a current of the gas flowing in one direction from the gas supplying portion 14 to the exhausting portion 15 in the space defined between the heating plate 12 and the top plate 18, thus performing a predetermined heating treatment. Thereafter, the wafer W having been subjected to the heating treatment will be transferred from the heating plate 12 to the cooling plate 13 after the top plate 18 is raised again. Subsequently, the wafer W will be transferred from the cooling plate 13 to the carrying mechanism (not shown) and then carried to a next step.
In such a heating apparatus, a cooling mechanism was provided for the cooling plate 13, such as by arranging a cooling pipe, for example, in the interior or at the bottom face thereof, to enable a cooling liquid to flow through the cooling pipe. Accordingly, the cooling plate 13 is required to have a thickness of about 10 mm. Therefore, between the heating plate 12 and the top plate 18, a gap greater than 10 mm should be required to meet both of such a thickness of the cooling plate 13 and the clearance for transferring the wafer W. However, such a large gap between the heating plate 12 and the top plate 18 may promote the entering of an external air into the gap, causing disturbance of the air current, thus compromising a desired one-way air current. Consequently, exhaustion of sublimates along a predetermined direction can not be performed satisfactorily, resulting in increase of the amount of attachment, onto the wafer W, of the sublimates produced from a resist liquid.
For this reason, the top plate 18 was configured to be optionally raised and lowered such that, when the wafer W is transferred between the cooling plate 13 and the heating plate 12, the top plate 18 is raised, while when the heating treatment is performed, it is lowered to a predetermined position. However, such raising and lowering motions of the top plate 18 may also disturb the air current in the interior of the heating apparatus. Accordingly, the exhaustion of sublimates can not be achieved satisfactorily, also causing attachment of particles onto the wafer W.
In order to enhance the throughput of the coating and developing apparatus in which the heating apparatus is incorporated, a relatively high throughput, for example, about 200 pieces, of wafers, as the number to be processed per hour, is needed also in the heating apparatus. To address this challenge, the working time except for the time required for heating the wafer W and for roughly removing heat just after the heating treatment, i.e., the overhead time, should be reduced as much as possible. However, for the aforementioned heating apparatus, the time required for the raising and lowering of the top plate 18 as well as for the transfer of the wafer W between the cooling plate 13 and the heating plate 12 should inevitably be the overhead time, resulting in reduction of the throughput.
To solve such a problem, we have attempted to construct a heating apparatus in which, rather than using the cooling plate 13 to carry the wafer W to the heating plate 12, a thin-type rigid arm can transfer the wafer W from the cooling plate 13 to the heating plate 12 so that the necessity of raising and lowering the top plate 18 of the heating plate 12 as well as of transferring the wafer W between the cooling plate 13 and the heating plate 12 can be eliminated. If the wafer W is of a size of 12-inches or greater, a warp may tend to occur in such a wafer W. In addition, in the case where the wafer W is placed 6n the heating plate 12 for the heating treatment, errors concerning carriage, such as displacement and falling of the wafer W, may tend to take place upon positioning such a warped wafer W on the heating plate 12. To address this problem, a method of heat-treating the wafer W while holding it in a floated state over the heating plate using a thin-type arm has been studied. With respect to this construction in which the wafer W is carried over the heating place using such a thin-type rigid arm, one example which carries the wafer using wires is described in Patent Document 1.
However, this Patent Document 1 does not suppose that the carrying mechanism can be applied to a heating apparatus including a cooling plate and a heating plate, that control of disturbance of an air current in a heating apparatus can be utilized to reduce the amount of attachment of particles to the wafer W, and that a heat treatment can be performed while holding the wafer W in a floated state over the heating plate using an arm. In addition, the Patent Document 1 does not touch on reduction of the overhead time required for the operation of the top plate 18 as well as for the transfer of the wafer to the heating plate. Therefore, it should be difficult for the Patent Document 1 to achieve the challenge which is a primary object of the present invention.
Document Cited
Patent Document 1: JITUKAISHO No. 62-17133, KOHO